Cobalt is too reactive to occur as a pure element in the earth. It is found in certain minerals. It is found with copper and nickel deposits. Normally the three metals are bonded to arsenic and sulfur. It is found as a byproduct (left over substance) when copper and nickel are produced. It is made by reaction with the sludge from copper and nickel processing.

Glass colored with cobalt. Cobalt is most commonly associated with the color blue and gray. Blue is shown here.

Cobalt is used in some types of steel. It hardens the steel. It is also used to make very strong tough alloys. These alloys are known as superalloys. Some cobalt compounds are used in the lithium-ion battery. Cobalt compounds were used as an artificial food coloring until 1971. It was discovered that it has harmful effects. It is used to make glass blue. It is also used as a catalyst. It is also used in some medicines.

The human body needs small amounts of cobalt for certain vitamins. Cobalt compounds are used to stop cyanide from poisoning the body.

People need cobalt compounds in small amounts, but cobalt is toxic in large quantities. Sometimes cobalt compounds were added to beer, and people that drank it were poisoned. It can cause skin irritation when touched.